Mol CO2 Research Articles

Protected supersonic separator performance against variable CO2 content on natural gas processing: Energy and sustainability analyses

In offshore oil-and-gas fields with high CO2 content, oil-and-gas processing entails recycling CO2 to the field for enhanced oil recovery. Despite blocking fossil CO2 ingress into the biosphere and improving oil production, this entails increasing %CO2 in oil-and-gas with time, challenging the processing plant. Supersonic separator is a compact gas processing solution that can simultaneously adjust water and hydrocarbon dew-points. But, supersonic nozzles can only work if sonic-throat flow occurs. In this work a supersonic nozzle sized to a high-pressure 25%mol CO2 feed is submitted to varying %CO2 from 5%mol to 80%mol under constant feed temperature/pressure and molar flow rate. Varying %CO2 affects nozzle performance with three possible outcomes: (i) feed is insufficient to reach sonic-throat flow, entailing no supersonic processing; (ii) feed is at design condition (25%mol CO2) and nozzle works tightly; and (iii) sonic-throat flow is achieved with a fraction of the feed; i.e., there is no room to process the rest. These apparent shortcomings of supersonic gas processing are examined and a control-scheme based on manipulating feed-pressure is proposed to circumvent feed deficit/excess. With the proposed feed-pressure adjustment to protect supersonic separator operation, energy and sustainability assessments are conducted to evaluate environmental and gas-fired power generation impacts from the supersonic processing of feeds with varying %CO2. Feeds with 10%mol/15%mol/20%mol CO2 have highest sustainability-degrees.

Growth Responses and Flowering of <i>Kalanchoe</i> Cultivars under Elevated CO<sub>2</sub> Concentration and Varying Daylength

This experiment was conducted to identify the morphological characteristics of elevated atmospheric CO2 concentration of Kalanchoe blossfeldiana cultivars under different daylength treatments, in order to apply the carbon reduction method. CO2 treatment took place between 22:00 and 04:00 with an average of 400 μmol·mol-1 (control) and 800 μmol·mol-1 on Kalanchoe blossfeldiana ‘Lion’ and ‘Fikalrudak’. The photoperiod was controlled using an 8 h (08:00 to 16:00), 12 h (06:00 - 18:00), and 16 h (04:00 - 20:00) light-dark cycle. The number of leaves increased more in plants under the 800 μmol·mol-1 treatment than those in the control, with a photoperiod of 8 h and 12 h in both K. ‘Lion’ and 8 h in K. ‘Fikalrudak’. Plant height was lower in plants treated with 800 μmol·mol-1 CO2 than under the control treatment with an 8-h photoperiod of 8 h, regardless of K. blossfeldiana cultivars. In K. ‘Lion’, immature leaf length and width increased more in plants treated with 800 μmol·mol-1 CO2 than in the control, with a photoperiod of 8 h and 12 h. However, the leaf length and width of K. ‘Fikalrudak’ was not affected by CO2 concentration. The nodes were produced primarily by increasing CO2 concentration to 800 μmol·mol-1, regardless of daylength and K. blossfeldiana cultivars. Flowering time was not affected by daylength, however, K. ‘Lion’ bloomed within the photoperiod of 8 h and 12 h and K. ‘Fikalrudak’ bloomed only under a photoperiod of 8 h. K. blossfeldiana cultivars bloomed effectively under less light availability, regardless of CO2 concentration. These results showed that a CO2-rich enrichment promotes leaf and node production of Kalanchoe blossfeldiana cultivars under short-day conditions. Since high concentration of CO2 enrichment can have an adverse effect on flowering quality, appropriate CO2 enrichment methods for the developmental stage and cultivars should be applied on a case-by-case basis.

Absorption of CO2 in aqueous blend of methyldiethanolamine and arginine

AbstractThe objective of this research is to study for the first time the effect of adding l‐arginine (Arg) amino acid on the solubility of carbon dioxide in aqueous solution of N‐methyldiethanolamine (MDEA). The study was carried out at different mixing ratios of MDEA and Arg at a total concentration of 2 moles per litre. The CO2 partial pressure varied from about 10 to 100 kPa, and the temperature varied from 293 K to 323 K. The experimental results showed improved solubility of CO2 with the addition of Arg at CO2 partial pressures below 20 kPa. However, for CO2 partial pressure of above 20 kPa, the addition of Arg caused a decrease in the solubility of CO2. The obtained loading data were correlated using a semiempirical (SE) vapour liquid equilibrium (VLE) model with an average absolute deviation (AAD) less than 4.1% between the predicted and the experimental values. An estimation of the heat of CO2 absorption in the solution was obtained using an analytical expression for ΔHabs derived from the SE model and was found to be in the range of 29‐ to 40‐kJ/mole CO2. From the finding of this work, it is anticipated that the studied novel blended solvent will effectively reduce CO2 capture costs as the CO2 content of most gas streams is less than 20% by volume, which is specifically true for natural gas and a large number of industrial flue gas streams.

Responses of net assimilation rate to elevated atmospheric CO2and temperature at different growth stages in a double rice cropping system

Effects of elevated atmospheric CO2 concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO2 and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO2 and/or temperature for three rotations of double rice in Jingzhou, Hubei Province. Liangyou 287 and Xiangfengyou 9 were used as rice cultivar for early rice and late rice, respectively. There were five treatments: UC, paddy field without OTC covering; CK, OTC with the similar temperature and CO2 concentration to field environment; ET, OTC with 2 ℃ temperature elevation; EC, OTC with 60 μmol·mol-1 CO2 elevation; ETEC, OTC with simu-ltaneous 2 ℃ temperature elevation and 60 μmol·mol-1 CO2 elevation. We measured aboveground biomass, leaf area index (LAI) and net assimilation rate (NAR) of dry matter under different treatments. Our results showed that elevated CO2 and/or temperature had no significant effects on NAR from transplanting to jointing, increased NAR from jointing to heading, but decreased NAR from heading to maturity (except for EC treatment in early rice). Elevated CO2 and/or temperature promoted leaf area development at all growth stages, with ETEC showing the highest increase in LAI except at maturity. Warming and CO2 enrichment jointly promoted dry matter accumulation at heading, with ETEC increasing aboveground biomass by 10.3%-39.8% and 23.6%-34.4% compared with CK in early rice and late rice, respectively. At maturity of early rice, elevated temperature partly offset the positive effects of elevated CO2 on aboveground biomass, as shown by a reduction of 3.2%-14.1% under ETEC compared with EC. Contrarily at maturity of late rice, co-elevation of CO2 and temperature further increased aboveground biomass, showing a synergistic interaction. Results from regression analysis showed that warming and CO2 enrichment had positive effects on NAR at vegetative stages of double rice, while warming showed negative effects on NAR at reproductive stages. Considering the dissimilarities in growth characteristics, growing periods and ambient temperature, elevated CO2 and temperature might increase dry matter production in the Chinese double rice cropping system.

The Highly Efficient Absorption of CO2 by a Novel DBU Based Ionic Liquid

A novel anion-functionalized protic ionic liquid (IL), [DBUH][Triz], has been synthesized from 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (Triz). Density (ρ) and viscosity (η) of [DBUH][Triz] at different temperatures have been measured and the influence of temperature has been analyzed quantitatively. Then, the applications of [DBUH][Triz] in CO2 absorption have been investigated. It has been detected that this ionic liquid, which was easily prepared, shows excellent reversibility and a high absorption capacity, about 1.5 mol CO2 per 1 mol of IL (about 0.3 g CO2 per 1 g of IL). In addition, the influence of temperature, pressure and moisture on the absorption performance of [DBUH][Triz] has been studied separately, indicating that absorption is promoted by lower temperature and higher CO2 pressure. In addition, the mechanism of chemical absorption at two active sites has been deduced based on quantum-chemical calculations and 13C NMR spectra coupled with IR spectra. Furthermore, the equilibrium constant of chemical absorption (K) was calculated from the CO2 capacity at different temperatures (T) and a good linear relationship between the natural logarithm of the equilibrium constant ln K and 1/T was obtained with R2 of 0.996. From the slope and intercept of the fitted straight line, the molar reaction enthalpy change (ΔrHm) and molar reaction entropy change (ΔrSm) were analyzed, indicating that the capture of CO2 is an exothermic process and the IL–CO2 complex is less ordered than the pure ionic liquid.

Kinetic evaluation of sterically hindered amines under partial oxy‐combustion conditions

AbstractBACKGROUNDCarbon capture and storage is considered one of the pillars that should support greenhouse gas (GHG) emission mitigation by 2050. In this sense, partial oxy‐combustion emerges as a promising alternative. Its advantages rely on the production of a higher CO2 concentration flue gas than these provided by conventional air‐firing processes. The use of higher CO2 concentrations should improve the solvent kinetic and the CO2 cyclic capacity.RESULTSThe kinetic behaviour of two representative sterically hindered amines, namely 2‐amino‐2‐methyl‐1‐propanol (AMP) and isophrondiamine (IF), were studied under partial oxy‐combustion conditions in a laboratory‐scale semi‐batch reactor. The CO2 concentration varied from 15%v/v to 60%v/v. The kinetic enhancement experienced by AMP at high CO2 concentration was slightly >60%, instead of 70–80% for IF. AMP also improved its CO2 absorption capacity by 24.7%, from 15%v/v to 60%v/v, almost doubled the improvements achieved by monoethanolamine (MEA). In the case of IF experiments, the CO2 loading increased ≈10% from 15%v/v to 60%v/v CO2 and it changed from 1.10 to 1.34 mol CO2 mol–1 solvent, representing a >20% increase.CONCLUSIONSThe presence of higher CO2 concentrations accelerated CO2 absorption and provided higher CO2 absorption rates. In addition, the evolution of the CO2 loading also exhibited higher values in the experiments using higher CO2 concentration flue gas. The steric hindrance causes a hybrid behaviour in these solvents, between both fast and slow kinetic solvents. The kinetic rates observed using AMP were slightly higher than MEA, but lower than IF which showed the fastest kinetics. © 2020 Society of Chemical Industry

Thermodynamic Evidence of Structural Transformations in CO2-Loaded Metal-Organic Framework Zn(MeIm)2 from Heat Capacity Measurements.

Metal-organic frameworks are a class of porous compounds with potential applications in molecular sieving, gas sequestration, and catalysis. One family of MOFs, zeolitic imidizolate frameworks (ZIFs), is of particular interest for carbon dioxide sequestration. We have previously reported the heat capacity of the sodalite topology of the zinc 2-methylimidazolate framework (ZIF-8), and in this Article we present the first low-temperature heat capacity measurements of ZIF-8 with various amounts of sorbed CO2. Molar heat capacities from 1.8 to 300 K are presented for samples containing up to 0.99 mol of CO2 per mol of ZIF-8. Samples with at least 0.56 mol of CO2 per mol of ZIF-8 display a large, broad anomaly from 70 to 220 K with a shoulder on the low-temperature side, suggesting sorption-induced structural transitions. We attribute the broad anomaly partially to a gate-opening transition, with the remainder resulting from CO2 rearrangement and/or lattice expansion. The measurements also reveal a subtle anomaly from 0 to 70 K in all samples that does not exist in the sorbate-free material, which likely reflects new vibrational modes resulting from sorbate/ZIF-8 interactions. These results provide the first thermodynamic evidence of structural transitions induced by CO2 sorption in the ZIF-8 framework.

Impacts on mechanical strength of chemical reactions induced by hydrous supercritical CO2 in Boise Sandstone

Geomechanics experiments were used to assess mechanical alteration of Boise Sandstone promoted by reactions with supercritical carbon dioxide (scCO2) and water vapor. During geologic carbon storage, scCO2 is injected into subsurface reservoirs, forming buoyant plumes. At brine-plume interfaces, scCO2 can dissolve into native brines, and water from brines can partition into scCO2, forming hydrous scCO2. This study investigates the effect of hydrous scCO2 on the strength of Boise Sandstone. Samples are first exposed to recirculating hydrous scCO2 for 24 h at 70 °C and 13.8 MPa scCO2 pressure. Samples are reacted with scCO2 with added water contents up to 500 mL. After scCO2 exposure, samples are deformed at room temperature under confining pressures of 3.4, 6.9, and 10.3 MPa. The results demonstrate that hydrous scCO2 induces chemical reactions in Boise Sandstone, with ions migrating from the solid into the hydrous scCO2 phase. At the longer time-scales, these reactions could lead to mechanical weakening in the samples; however, on the scale of our experiments, the strength changes are within sample variability. Because the solubility of water in scCO2 is extremely low (0.008 mol H2O per 1 mol CO2), the mineral dissolution of Boise Sandstone was under 0.002 wt.%. Additionally, mineral grains and pore throats in Boise Sandstone are cemented with quartz, which is not susceptible to dissolution at these conditions. Our results indicate that humidity in scCO2 plumes is unlikely to sustain chemical reactions and induce long term strength changes in quartz cemented sandstones due to resistant mineralogies and low water solubility.

Photochemistry and photoprotection of ‘Gem’ avocado (Persea americana Mill.) leaves within and outside the canopy and the relationship with fruit maturity

A reduction in photosynthesis results in a reduced CO2 assimilation rate and availability of carbohydrates essential for fruit growth and development. This study determined photosynthetic efficiency and photoprotection mechanisms within and outside leaf canopy positions in ‘Gem’ avocado orchards and their relationship with avocado fruit maturity. The study was conducted in a commercial orchard at Everdon Estate in KwaZulu-Natal, South Africa. A total of 15 eight-year-old avocado trees (cv. Gem) were selected in a completely randomised design with three replicates, with each replicate consisting of five trees. Data were collected bi-weekly on photosynthetic rate (A), effective quantum efficiency of photosystem II (ϕPSII), stomatal conductance (gs), transpiration rate (T), electron transport rate (ETR), minimum fluorescence (Fo’), maximum fluorescence (Fm’), variable fluorescence (Fv’), intrinsic water use efficiency (WUEi), instantaneous water use efficiency (WUEins), intercellular CO2 concentration (Ci) and photochemical quenching (qP) from full bloom to fruit physiological maturity (∼25 % dry matter content (DM)). The results showed that leaves from the outside position had higher A (29.46 mol CO2 m−2s-1); gs (0.078 mol CO2 m−2s-1); ΦPS II (0.32); and qP (0.52) compared to those within the canopy position with lower A (19.27 mol CO2 m−2s-1); gs (0.0037 mol CO2 m−2s-1); ΦPS II (0.044) and qP (0.075), respectively. Contrastingly, chlorophyll fluorescence and photoprotection parameters were higher within the canopy than on the outside, suggesting that the greater proportion of energy accumulated within the canopy was used for photoprotection other than photochemistry. Photosynthetic rate (A), gs, Ci, T, WUEi and WUEins, correlated significantly with mesocarp dry matter (DM), while all other parameters correlated poorly. The high photosynthetic efficiency of leaves from outside the canopy resulted in an average DM of 28.9 % compared to 26.9 % of fruit within the canopy. The present findings suggest that reduced photosynthetic efficiency of ‘Gem’ avocado within the canopy position does not compromise fruit DM by reserving more energy for photoprotection; however, it delays maturity by about two weeks.

Assessing the prevalence, products, and pathways of dissolved organic matter partial photo-oxidation in arctic surface waters.

In sunlit waters, photodegradation of dissolved organic matter (DOM) yields completely oxidized carbon (i.e., CO2) as well as a suite of partially oxidized compounds formed from oxygen incorporation (i.e., partial photo-oxidation). Of these two groups of DOM photo-products, more studies focus on CO2 (a greenhouse gas) than on partially oxidized DOM, which is likely a diverse group of compounds with poorly constrained roles in aquatic carbon cycling or biogeochemistry. The objective of this study is to address knowledge gaps on the prevalence, products, and pathways of DOM partial photo-oxidation. Here we traced the photochemical incorporation of isotopically labelled 18O2 into DOM isolated from Alaskan Arctic surface waters using high-resolution mass spectrometry. Complete and partial photo-oxidation of DOM was also quantified as CO2 production and O2 consumption. The majority of 18O-containing partial oxidation photo-products were classified as carboxylic rich alicyclic molecules (CRAM) and overlapped in composition with previously reported photo-products known to result from the oxidation of DOM by singlet oxygen. These results support a previously proposed hypothesis that photo-oxidation by singlet oxygen may contribute to the formation of CRAM, a compound class of DOM ubiquitously observed in surface waters. The novel application of an isotopic tracer for oxygen incorporation with a mass balance approach to quantify complete and partial photo-oxidation of DOM revealed that less than one mol of O2 is required to produce one mol of CO2. A sensitivity analysis based on this new knowledge demonstrated that the magnitude of DOM partial photo-oxidation may be underestimated by up to four-fold. Consequently, partial photo-oxidation likely plays a more prominent role in shaping DOM composition in sunlit waters of the Arctic than previously understood. Therefore, partial photo-oxidation should be increasingly incorporated into the experimental framework of studies focused on DOM composition in surface waters.

Physiological assessment of iron and zinc biofortification on growth and yield parameters of sweet corn

Field experiment was carried out during kharif 2017 and 2018 in black soil at farmer field at Kumarnahally village, Huvina hadagali Tq, Bellary District representing the Northern Dry Zone (Zone-II) which is located at latitude of 15.04’ N, longitude of 75.94' E and 561 meters which is above mean sea level to study the physiological assessment of iron and zinc biofortification on growth and yield parameters of sweet corn (Zea mays L. Saccharata) to evaluate and analysis of sweet corn through biofortification to achieve higher growth and yield parameters. Pooled data both years indicated that seed treatment with ZnSO4 @ 0.5 % + FeSO4 @ 0.5 % and foliar spray of ZnSO4 @ 1.0 % + FeSO4 @1.0 % recorded significantly higher total dry matter (196.3, 203.8 and 200.1 g plant-1 at 30, 60 DAS and at harvest, respectively) and also higher photosynthetic rate (17.2, 33.5 and 32.7 µ mol CO2 m-2 s-1 at 30, 60 DAS and at harvest respectively. Similarly Fresh cob yield was noticed with seed treatment by ZnSO4 @ 0.5 % & FeSO4 @ 0.5 % and foliar spray of ZnSO4 @ 1.0 % & FeSO4 @1.0 % which was on par with seed treatment with ZnSO4 @ 0.5 % + foliar spray of ZnSO4 @ 1.0 % + FeSO4 @1.0 % during the year 2017, 2018 and pooled data.

Study of carbon dioxide and methane adsorption on carbon molecular sieves, raw and modified by waste engine oil

In this study, a carbon molecular sieve (CMS) was synthesized from walnut shells, followed by physical activation of the carbon content of the CMS. Adsorption of CO2 and CH4 onto raw and acid treated adsorbents were investigated using two sizes, 300?600 and 600?1180 ?m. The adsorbents were impregnated with two solvent mixtures of waste engine oil with kerosene and with thinner at a proportion of 1:1 at 25?C. The highest adsorption for CO2 and CH4 was obtained at the suitable size of a group of CMS(A) adsorbents, with acid treated adsorbents being more efficient than the raw adsorbents. The acid treated CMS(A-3) sample adsorbed 0.925 mol CO2 g-1 and 0.353 mol CH4 g-1. The results indicated that by decreasing the granulation size of group CMS(R) adsorbents, the adsorption capacities for CO2 and CH4 were reduced while increasing the granulation size of group CMS(A) adsorbents resulted in an enhancement in the adsorption capacity for CO2 and CH4. Moreover, acid treated adsorbents achieved enhanced adsorption capacity for CO2 and CH4. Further modifications reduced the adsorption capacity for CO2 and CH4 in impregnated adsorbents, due to a decrease in surface area, pore volume and pore size of the adsorbent.

Spatiotemporal Variability and Sources of DIC in Permafrost Catchments of the Yangtze River Source Region: Insights From Stable Carbon Isotope and Water Chemistry

AbstractRiverine dissolved inorganic carbon (DIC) exports play a central role in the regional and global carbon cycles. Here, we investigated the spatiotemporal variability and sources of DIC in eight catchments in the Yangtze River source region (YRSR) with variable permafrost coverage and seasonally thawed active layers. The YRSR catchments are DIC‐rich (averagely 25 mg C L−1) and export 3.51 g m−2 yr−1 of DIC. The seasonal changes of temperature, active layer, flow path, and discharge can alter DIC and stable carbon isotope of DIC (δ13C‐DIC). The most depleted δ13C‐DIC values were found in the thawed period, suggesting the soil‐respired CO2 during the active layer thaw period can promote bicarbonate production via H2CO3 weathering. Spatially, δ13C‐DIC values increased downstream, likely due to CO2 outgassing and changed permafrost coverage and runoff. We found that evaporite dissolution and silicate weathering in the seasonally thawed active layer contributed 44.2% and 30.9% of stream HCO3‐, respectively, while groundwater and rainwater contributed 16.7% and 7.3% of HCO3‐, respectively. Pure carbonate rock weathering played a negligible role in DIC production. These results were compatible with δ13C‐DIC source approximation results. Silicate weathering increased from initial thaw to thawed period, reflecting the active layer thaw and subsequent hydrology change impacts. Silicate weathering consumed 1.25 × 1010 mol of CO2 annually, while evaporite dissolution may produce CO2 and neutralize this CO2 sink. This study provides new understanding of the riverine DIC export processes of the YRSR. As permafrost degrades, the quantity, sources, and sinks of riverine DIC may also change spatiotemporally.

Isolating substituent effects in Re(I)-phenanthroline electrocatalysts for CO2 reduction

The development of highly-active molecular electrocatalysts for reducing CO2 to value-added products requires an intimate knowledge of the structural and electronic features surrounding the active site. We previously illustrated how electronic modifications to fac-[ReI(R2phen)(CO)3Cl] electrocatalysts (R2phen = 2,9-disubstituted-1,10-phenanthrolines) strongly dictate CO2 reduction; more specifically, introducing methoxy substituents at both the ortho/para positions of a phenyl ring attached to phenanthroline generated high catalytic activity. In the current work, we have prepared four structurally-related Re(I) electrocatalysts to isolate the electronic effects associated with each methoxy group’s positioning around the phenyl ring (i.e. none, ortho, meta, or para). The diimine ligands 2,9-diphenyl-1,10-phenanthroline (Ph2phen), 2,9-bis(2,6-dimethoxyphenyl)-1,10-phenanthroline ((2,6-dmp)2phen), 2,9-bis(3,5-dimethoxyphenyl)-1,10-phenanthroline ((3,5-dmp)2phen), and 2,9-bis(4-methoxyphenyl)-1,10-phenanthroline ((4-mp)2phen) were prepared, and the subsequent fac-[ReI(R2phen)(CO)3Cl] complexes were synthesized, characterized, and studied for electrocatalytic CO2 reduction. Following 90 min electrolysis at Eapp = −2.55 V vs. Fc+/0 in DMF solvent, the ortho methoxy-substituted analogue (labeled Re((2,6-dmp)2phen)) produced 35 μmol CO, corresponding to a turnover number = 14 (TON = mol CO per mol Re catalyst) and a Faradaic efficiency = 84% (F.E. = mol CO per mol electrons). The remaining Re electrocatalysts produced significantly lower levels of CO (Re(Ph2phen): 1.8 μmol CO; Re((3,5-dmp)2phen): 2.4 μmol; Re((4-mp)2phen): 4.2 μmol CO), emphasizing the important electronic contribution that ortho substituted methoxy groups provide towards enhancing electron density at the Re active site to rapidly, and selectively, convert CO2 substrate to CO product.

Mechanism of oxides reduction during bubbling of copper-smelting slags by CO–CO<sub>2</sub> gas mixtures

The paper suggests a mechanism of simultaneous oxide reduction from multicomponent copper-smelting slags during their bubbling with CO–CO2 reducing mixtures and provides a numerical algorithm developed to implement this mechanism as a mathematical model. The first feature of the suggested mechanism is a statement that the total speed of the overall reduction process is determined by CO consumption during its interaction with oxygen ions formed in slag oxide dissociation. The second feature is a statement about equilibrium achieved between slag, alloy and gaseous phase according to the system oxidizing potential reached at every instant. The paper demonstrates a satisfactory agreement between calculated and experimental data obtained when reducing industrial coppersmelting slags at 1300 °С and СО/СО2 = 4, 6, 156, and using the first-degree kinetic equation regarding the difference between initial and equilibrium CO contents in the gaseous phase. A generalized kinetic constant of the multicomponent slag reduction reaction rate is calculated as k = 2.6·10–7, moles CO /(cm2 · sec·%) at 1300 °С. It is shown that during industrial multicomponent slag reduction, reduction speed of copper (I) oxide and magnetite are high and close to maximal ones as early as at the first minutes of slag bubbling with reducing gas. At the same time, for Fe(II), lead and zinc oxides they are low at the first minutes of the process, and increase gradually to reach their maximum, and then decrease again up to near-zero values as the supplied gas and melt come to equilibrium. Generally, oxide reduction speed naturally decreases with approaching to equilibrium between the initial gas and liquid phases, and this should be taken into account when designing continuous slag depletion processes.

Summertime Atmospheric Boundary Layer Gradients of O2 and CO2 over the Southern Ocean

AbstractWe present airborne observations of the vertical gradient of atmospheric oxygen (δ(O2/N2)) and carbon dioxide (CO2) through the atmospheric boundary layer (BL) over the Drake Passage region of the Southern Ocean, during the O2/N2 Ratio and CO2 Airborne Southern Ocean Study, from 15 January to 29 February 2016. Gradients were predominately anticorrelated, with excesses of δ(O2/N2) and depletions of CO2 found within the boundary layer, relative to a mean reference height of 1.7 km. Through analysis of the molar ratio of the gradients (GR), the behavior of other trace gases measured in situ, and modeling experiments with the Community Earth System Model, we found that the main driver of gradients was air‐sea exchange of O2 and CO2 driven by biological processes, more so than solubility effects. An exception to this was in the eastern Drake Passage, where positive GRs were occasionally observed, likely due to the dominance of thermal forcing on the air‐sea flux of both species. GRs were more spatially consistent than the magnitudes of the gradients, suggesting that GRs can provide integrated process constraints over broad spatial scales. Based on the model simulation within a domain bounded by 45°S, 75°S, 100°W, and 45°W, we show that the sampling density of the campaign was such that the observed mean GR (± standard error), −4.0± 0.8 mol O2 per mol CO2, was a reasonable proxy for both the mean GR and the mean molar ratio of air‐sea fluxes of O2 and CO2 during the O2/N2 Ratio and CO2 Airborne Southern Ocean Study.

Impact of Nitrogen Addition on Physiological, Crop Total Nitrogen, Efficiencies and Agronomic Traits of the Wheat Crop under Rainfed Conditions

Optimizing nitrogen (N) application timings and rate can improve nutrient uptake and nutrient efficiencies in wheat, particularly under rainfed conditions. Climatic stress in the form of high temperature and drought resulted in the decreased crop physiological traits, hastened maturity and, ultimately, caused lower grain yield. The impact of N application rates as full and split dose at three diverse locations of rainfed Pothwar, Pakistan was studied through field experiments for two years (2013–14 and 2014–15). Treatments include T1 = control (no fertilizer applied), full dose of N applied at the time of crop sowing, i.e., T2 = 50 kg N ha−1, T3 = 100 kg N ha−1 and T4 = 150 kg N ha−1, and split application of N at different timings at different stages of the crop, called split application of N, i.e., T5: application of 50 kg N ha−1 (15 kg N ha−1 (sowing, BBCH (Biologische Bundesanstalt Bundessortenamt und Chemische Industrie) 0): 20 kg N ha−1 (tillering, BBCH20): 15 kg N ha−1 (anthesis, BBCH 60), T6: application of 100 kg N ha−1 (30 kg N ha−1 (sowing, BBCH 0): 40 kg N ha−1 (tillering, BBCH 20): 30 kg N ha−1 (anthesis, BBCH 60) and T7: application of 150 kg N ha−1 (45 kg N ha−1 (sowing, BBCH 0): 60 kg N ha−1 (tillering, BBCH 20): 45 kg N ha−1 (anthesis, BBCH 60). The three study sites were Islamabad (high rainfall with optimum temperature), University Research Farm (URF)-Chakwal Road, Koont (medium rainfall with moderate temperature), and Talagang (low rainfall with high temperature). Results revealed that the highest stomatal conductance (0.80 mole H2O m−2 s−1), net photosynthetic rate (20.07 μmole CO2 m−2 s−1), transpiration rate (9.58 mmole H2O m−2 s−1), intercellular CO2 concentration (329.25 μmole CO2 mol−1 air), SPAD values (58.86%) and proline contents (35.42 μg g−1) were obtained from split application of N (T6 = split N100) compared to control and full dose N treatments. Among the sites, these physiological traits remained highest at Islamabad and lowest at Talagang, while between the years, the maximum values of the measured parameters were obtained during 2013–14. A similar trend was observed for crop total N, N efficiencies, and agronomic traits of the crop. The results suggested that the optimum N application rate at appropriate timings can help to harvest the real benefits of N. The split dose resulted in the maximum performance of the crop from the physiological parameters to the agronomic traits of the crop.

Multicycle Study on Chemical Looping Combustion with a CaSO4-CaO Mixed Oxygen Carrier

Abstract Chemical looping combustion (CLC) is a carbon capture technology which enables CO2 capture with low net efficiency penalty. Calcium sulfate (CaSO4) is an optional oxygen carrier for commercial use, but its usage is limited due to sulfur dioxide (SO2) emission. This study approaches this issue by adding CaO species into the CaSO4 oxygen carrier to inhibit the release of SO2 from CaSO4 oxygen carrier. In this study, the cyclical tests of a CaSO4-based oxygen carrier under alternating reducing and oxidizing conditions were performed at 900 °C and 800 °C respectively in a tubular furnace reactor at atmospheric pressure. The effects of reducing gas concentration and molar ratio of CaO/CaSO4 on the performance of CaSO4-CaO oxygen carrier were studied in terms of CO2 yields, Environmental factors of SO2 and COS, molar ratios of gas sulfides to CO2 generated in fuel reactor, and molar ratios of SO2 and COS to total carbon inlet. The use of CaO additive increased the yields of CO2 obviously. The release of COS in the fuel reactor and SO2 in the air reactor decreased, but while the overall release of SO2 in the fuel reactor increased. However, for per mole CO2 generation, less gas sulfides released from the fuel reactor. High concentrations of CO were beneficial for CO2 production and a low SO2 environmental factor, and meanwhile, the molar ratios of SO2 released to inlet CO {{\text{n}}_{{\text{S}}{{\text{O}}_2}}}/{{\text{n}}_{{\text{CO}}}} decreased. However, it led to a drop in CO2 yield and an increase in COS environmental factor. As a whole, the use of CaO additive and higher CO concentration both accelerated the parallel CaSO4 reductions in fuel reactor, especially the selectivity of CaSO4 reduction to CaS.

Temporally-variable productivity quotients on a coral atoll: Implications for estimates of reef metabolism

Measurements of net ecosystem productivity (NEP) and calcification (NEC) from contemporary coral reefs provide a baseline for monitoring the impacts of future stressors like ocean acidification and sea-surface warming. However, separating secular trends from natural variability requires NEP and NEC records across a wide range of spatial and temporal scales. One promising way to make these measurements is with autonomous pH and O2 sensors. Crucially, the accuracy of this approach relies on knowledge of the in situ ecosystem productivity quotient (Q), which indicates the moles of O2 consumed per mole CO2 produced. Using co-located measurements of total dissolved inorganic carbon (DIC), total alkalinity, and dissolved O2, we empirically determined Q during a three-year field campaign on Tetiaroa Atoll, French Polynesia. Empirical values of daily net Q (−1.02 ≤ Qnet ≤ −0.47) frequently differed from both the canonical value of −1.45 for the ocean and the value of −1 often assumed for tropical reef ecosystems. Furthermore, Q changed on hourly timescales, and integrated daily values differed between days. We hypothesize that captive bubbles on the surfaces of coral, macroalgae and other substrates can explain these variations in Q, with other influential mechanisms being mixing between parcels of water, sedimentary denitrification, and ammonium-fueled primary productivity. Our findings, which are robust to changes in the model that is used to correct for advection and gas exchange, as well as changes in model parameters, suggest that future investigations of metabolism on reefs should be based on measurements of carbonate chemistry variability, rather than O2 evolution. Otherwise, large biases in NEP and NEC could result (> 40%).

Physiological Response of Upland Rice Varieties to Furrow with Organic Matter on Agroforestry System with Kayu Putih (Melaleuca leucadendra L.)

<p>Drought is one of the major limitations in dry land cultivation. Drought affects plant physiology processes such as photosynthesis, respiration, mineral and water transportation, and transpiraton, briefly called drought stress. Drought stress can be avoided by managing environment. Furrow containing organic matter for rain fed rice has been the subject of many studies, with special emphasis on soil moisture. This research is aimed to know the effects of the furrow containing organic matter on physiological responses of several upland rice varieties on agroforestry system based on <em>k</em><em>ayu putih</em> (cajuput). The experimental design applied the strip plot design. The vertical factor is the furrow system of treatment consisting of 2 levels i.e. without furrow + without organic matter and furrow + organic matters. The horizontal factors are the upland rice varieties consisting of 3 varieties i.e. Situ Patenggang, Situ Bagendit and Ciherang. The collected data were analyzed by Analysis of Variance (ANOVA) applying a level of significance α = 5%. Whenever significant differences among treatments were found, further analysis was carried out by applying the Tukey's HSD (Honestly Significant Difference) test α = 5% levels. The result shows that drought affects plant physiology and can be avoided by using furrow containing organic matters. Situ Patenggang with furrow containing organic matters has the higher physiology capability, it had photosynthesis 387.18 µmol CO<sub>2 </sub>per clump s<sup>-1</sup>, transpiration 3038.50 mg per clump per secondand CO<sub>2 </sub>721.11 mol CO<sub>2</sub> clump per mol. There different plant requirements for Cu between varieties.</p>